Carcinogenicity or toxicity?

Criticizing the Séralini
study on the grounds that it does not meet the criteria for a carcinogenicity
study is equivalent to criticizing a cat for not being a dog.

According
to Dr Hayes’ retraction statement, retraction was justified because “The low
number of animals, and the strain selected, rendered the conclusions
unreliable.”[1]

Other critics of the study, including the
European Food Safety Authority (EFSA),[2]
have voiced the same views.

However,
these arguments are specious and derive from the false premise that Séralini
and colleagues conducted a carcinogenicity study – which they did not. The
authors clearly stated in the title of the paper and in the introduction that
this was a long-term (chronic) toxicity study, not a carcinogenicity study.

Indeed, the authors affirmed the need to follow up the tumour observations in a
separate, dedicated carcinogenicity study, which would include a larger sample
size, in their “Answers to Critics”,[3]
published in FCT prior to the retraction decision.

Carcinogenicity studies have a different
design from chronic toxicity studies. They require larger groups of animals,[4]
typically 50 per sex per group. This is in order to achieve statistical
significance – a higher degree of certainty or conclusiveness – in their
results, and
also to prevent a “false negative” conclusion: that is, failing to find a rare
toxic effect because too few animals are used.

Chronic toxicity studies such as Séralini’s
require fewer animals. For example, the OECD chronic toxicity protocol no. 452
recommends 20 animals per sex per group but only requires 10 per sex per group
to be analyzed for blood and urine chemistry.[5]
This is the same number of animals that Séralini used in total and the same
number that Monsanto analyzed for blood and urine chemistry in its 90-day study
on the same GM maize.[6]

The Sprague-Dawley strain of rat used by
Séralini and colleagues is routinely used for chronic toxicity and long-term
carcinogenicity studies performed by both industry and academic scientists.[7]

Criticizing
the Séralini study on the grounds that it does not meet the criteria for a
carcinogenicity study is equivalent to criticizing a cat for not being a dog.
It is an irrelevance that diverts attention from the importance of the
toxicological findings.

[3] Séralini
GE et al. (2013). Answers to critics: Why there is a long term toxicity due to
NK603 Roundup-tolerant genetically modified maize and to a Roundup herbicide.
Food and Chemical Toxicology 53:
461-468.